I may be wrong but I think you need a wireless computer so that you can just hook the ethernet cable from the xbox to the pc's empty slot.

Ive never hooked it up that way but I think thats how its done. Some others will chime in Im sure.

 

there shouldn't be a cord that comes with live. There is an ethernet cord that comes with the 360.

There are only 2 ways to connect that I know of:

A: you plug an ethernet cord (gray cord that comes with the console) from the xbox to a network router that is already connected to the internet ( or straight to a high speed modem if you do not use internet for anything else)

Router Connection

B: use a wireless network adapter made for the 360, which will connect to any WIFI signal present in your home.

Wireless Connection to Xbox Live


Overview: Guide to Home Networking: Introduction